Aromatic carbonate resins such as polycarbonate resins are thermoplastic resinous materials possessing many excellent physical and chemical properties which render them useful in a wide range of applications. They exhibit for example excellent properties of toughness, impact resistance, heat resistance and dimensional stability, optical clarity or non-opaqueness and physiological inertness. Also of particular interest the aromatic carbonate resins are generally thought to be relatively non-flammable. However, with the additional applications of aromatic carbonate resins and such fields as computer housings, aircraft interiors, and other utilities which require significantly higher levels of non-flammability, flame retardant systems for the aromatic carbonate polymers had to be discovered. Halogenated systems have been found to be successful for flame retardant aromatic carbonates. Additionally, small quantities of flame retardant salts, generally those with a sulphonic acid grouping thereon have been found to also be successful in flame retarding the aromatic carbonates. It has also been found that small quantities of fluorinated polyethylenes such as fibrillar teflons have also been necessary to bring about a very low level of flammability as measured by the underwriter laboratory 94 test system which utilizes the measurement of flaming drips as well as flameout time of the particular plastic being studied. Additionally it has been shown that the thinner the section of aromatic carbonate polymer being flame retardant, the more difficult it is to achieve the maximum class of flame retardation under the UL 94 test system, that is no flamming drips and a flame-out time of 5 seconds or less.
Not only have additive systems been developed for the aromatic carbonate polymers but additionally there have been attempts to modify the polymer backbone to bring about increased flame retardancy. For example in EPA 85 103 914 allylic groups have been added to the phenolic moieties of the dihydric phenol in an attempt to bring about greater flame retardancy. Additionally silicones with Group II A organo-metallic salts are claimed as flame retardant additives for polycarbonate (U.S. Pat. No. 4,387,176). It has also been well known to add siloxane units to the backbone of aromatic carbonate polymer systems to bring about greater processability as well as other features, see Vaughn U.S. Pat. No. 3,189,662 as well as Vaughn U.S. Pat. No. 3,419,635.
It has now been discovered that aromatic carbonate polymers with siloxane units built into the backbone wherein the silicon atom carries a vinyl group successfully flame retards the aromatic carbonate polymer. While so doing the general properties of the aromatic carbonate polymer system such as impact resistance, tensile strength, modulus and transparency in general maintain their usually observed levels or have relatively low reductions.